1. Field of the Invention
The present invention relates to a handle operating mechanism in a circuit breaker equipped with a rotary operation handle, which is intended to be applied to a wiring molded-case breaker or the like.
2. Description of the Related Art
First, FIGS. 5 to 7 show a conventional configuration of a circuit breaker equipped with a rotary operation handle as mentioned above. First, in FIG. 5, the reference numeral 1 represents a body case of the circuit breaker, constituted by a lower case 1a and an upper cover 1b; 2, a breaking portion for a main circuit contact, incorporated in a bottom portion of the lower case 1a; 3, a contact switching mechanism portion for the breaking portion 2; 4, an overcurrent tripping device; 5, a rotary operation handle attached to the upper surface of the cover 1b; and 6, a gear mechanism for establishing linkage between the operation handle 5 and the contact switching mechanism portion 3.
Here, as shown in FIG. 6, the gear mechanism 6 is constituted by the combination of a rotary gear (driving gear) 8 connected to a shaft of the operation handle 5, and a toggle gear 9 having an axis perpendicular to that of the rotary gear 8 and attached to the contact switching mechanism portion 3. On the other hand, the contact switching mechanism portion 3 is constituted by a toggle link mechanism 3a linking with the toggle gear 9, a switch lever 3c urged by a main spring 3b, a latch mechanism, and so on. In addition, as shown in FIG. 7, the breaking portion 2 is constituted by a fixed contact 2a, a bridging movable contact 2b, a movable contact holder 2c, a contact spring 2d, an arc-suppressing plate 2e, and so on. The switch lever 3c faces the upper surface of the movable contact holder 2c. Incidentally, contacts corresponding to three phases are incorporated in the breaking portion 2, and movable contacts 2b and contact springs 2d for the respective phases R, S and T are mounted and supported in the movable contact holder 2c so as to be arrayed left and right.
In such a configuration, when the operation handle 5 is rotated from an OFF position to an ON position, the toggle link mechanism 3a pushes down the rear end of the switch lever 3c through the gear mechanism 6. As a result, the switch lever 3c rotates counterclockwise so as to store energy in the main spring 3b. In the breaking portion 2, the movable contact 2b urged by the contact spring 2d comes into contact with the fixed contact 2a so as to close the main circuit. On the contrary, when the operation handle 5 is rotated from the ON position to the OFF position, the toggle link mechanism 3a operates in a reverse direction to the above-mentioned one so as to release the switch lever 3c from restriction. As a result, the switch lever 3c is driven to rotate clockwise by the stored energy of the spring force of the main spring 3b to open the movable contact 2b through the contact holder 2c. Also when the latch mechanism of the contact switching mechanism portion 3 is released by the operation of the overcurrent tripping device 4 so as to carry out tripping, the main circuit contact is opened likewise. In this case, the operation handle 5 rotates from the ON position and stops in a TRIP display position.
In addition, FIGS. 8A and 8B are diagrams showing a conventional structure of the handle operating mechanism of the above-mentioned circuit breaker. The rotary gear 8 has teeth 8a gearing with the toggle gear 9 and is coupled with a shaft 5a of the operation handle 5, so that the shaft 5a is fit into the rotary gear 8. On the other hand, the toggle gear 9 is attached to the contact switching mechanism portion 3 so that the axis of the toggle gear 9 crosses the axis of the rotary gear 8 at right angles. Thus, the toggle gear 9 is linked with the above-mentioned toggle link mechanism so that the teeth of the toggle gear 9 gear with the teeth 8a of the rotary gear 8. Incidentally, the reference numeral 10 represents a return spring for urging the operation handle 5 toward the OFF position.
In the slow-make type circuit breaker as described above, the contact switching mechanism portion 3 is driven synchronously with the manual operation of the rotary operation handle 5 so as to open and close the main circuit contact. In such a slow-make type circuit breaker, particularly if the handle is rotated slowly toward the ON position at the time of operation to make the contact, there may occur a slight temporal gap among the respective phases in the timing with which the movable contact comes into contact with the fixed contact. Thus, there is a fear that the temporal gap causes an obstacle to start-up control of an electric motor or the like. In order to avoid such a disadvantage so as to close the contacts in the respective phases at the same timing, it is necessary for an operator to carry out an operation to rotate the operation handle at a high speed at the time of make of the circuit breaker.
On the other hand, as artificial quick-make means for forcibly increase the operating speed of the handle at the time of contact make of the circuit breaker, there has been hitherto developed a circuit breaker with an interrupt mechanism such as a cam type one in which an operation handle is passed through while the operating force acting on the operation handle is forcibly increased in the middle of a make stroke of the handle. In such a circuit breaker, there has been a drawback in durability or reliability because such an artificial quick-make function is lost before the circuit breaker body reaches its switch life of number of times.
It is therefore an object of the present invention to provide a handle operating mechanism in a circuit breaker in which artificial quick-make means for forcibly increasing the operating speed of a handle at the time of contact make is constituted by a mechanism which is excellent in reliability and durability and exhibits effects on assembling performance and unification of parts.
In order to achieve the above object, according to the present invention, there is provided a handle operating mechanism in a circuit breaker equipped with a rotary operation handle for driving a contact switching mechanism in synchronism with manual operation to thereby open/close a main circuit contact, wherein a ratchet unit is provided as artificial quick-make means for forcibly increasing operating force of the operation handle in the middle of a make stroke for ON-operation of the contact, the ratchet unit being constituted by a convex cam which is synchronously gearing with the operation handle, a ratchet which is disposed at a point close to an ON position of the operation handle so as to be lateral to a rotary movement path of the cam, and a driving spring which presses a claw portion of the ratchet from behind so as to thrust the claw portion toward a movement locus of the cam. Specifically, the ratchet unit is configured in the following modes.
Preferably, the cam and the ratchet are made of metal which is high in abrasion resistance.
Preferably, the ratchet is a lever which is pivotally supported at one end thereof and in which a convex claw portion and a seat for the driving spring are formed at a forward end side of the lever, and the ratchet is disposed in tensile claw relationship with a moving direction of the cam at the time of ON-operation of the handle.
Preferably, the ratchet and the driving spring are incorporated in a discrete ratchet case, and the ratchet case is fabricated inside a case cover of a circuit breaker body.
Preferably, a bearing hole of a ratchet spindle formed in the ratchet case is formed into a long hole, and the ratchet receives pressure force of the cam at the time of OFF-operation of the operation handle so as to retreat along the long hole.
Preferably, the cam and the ratchet are formed as common parts, and spring force of the driving spring is set in accordance with another kind of circuit breaker different in rating.
In the above-mentioned configuration, when the operation handle is rotated from an OFF position to an ON position at the time of make of the circuit breaker, in the middle of the rotation, the cam linking with the operation handle abuts against the ratchet urged by the spring so as to receive resistance force (braking force). Here, when operating force acting on the handle is increased so that the cam thrusts the ratchet away to thereby get over the ratchet, the resistance force acting on the operation handle disappears so that the handle becomes light suddenly. Consequently, the operation handle rotates quickly at a dash to the ON position. In synchronism with this handle operating speed, the contact switching mechanism portion operates to close the main circuit contacts for the respective phases in accordance with the contact timing.
In this case, when the cam and the ratchet are made of metal which is high in abrasion resistance, the durability is improved and there is no fear that an artificial quick-make function is lost before the circuit breaker reaches its switch life of number of times. Thus, the reliability is improved. In addition, when the ratchet mechanism is formed into a unit and fabricated in a case of a circuit breaker body, while the driving spring is combined in accordance with another kind of circuit breaker different in rated current, the assembling performance can be improved, and unification of the parts can be attained.
Further, when the bearing hole of the ratchet spindle formed in the ratchet case is formed into a long hole so that the ratchet receives pressure force of the cam at the time of OFF-operation of the operation handle so as to retreat along the long hole, the operation handle passes through the ratchet mechanism without suffering large resistance force from the ratchet mechanism at the time of OFF-operation of the circuit breaker. Thus, the operation handle can be rotated to the OFF position easily with comparatively light force.